Teaching about Greenhouse Gas Behavior Helps to Address Student Misconceptions

Encouraging personal action and support for climate change mitigation and greenhouse gas emissions reduction initiatives is vital to future sustainability. If more people have a better understanding of the greenhouse effect, then they are more likely to understand why the reduction of greenhouse gas emissions is important for slowing down or mitigating global warming. Previous studies have shown that using constructivist-based learning, a teaching technique that builds on and connects with a student's existing understanding of a subject, better addresses misconceptions and helps students have a more complete understanding of a subject. In this study, the researchers conducted a constructivist-style lesson and analyzed student knowledge of the greenhouse effect. Their goals were to find out what concepts help students have a more complete scientific understanding of the greenhouse effect and what existing misconceptions about the greenhouse effect are easier or harder to change.

This research took place at a North American university. The researchers completed a 30-minute greenhouse effect lesson with 164 undergraduate students in an introductory oceans and atmosphere course. Their lesson focused on the molecular behavior of greenhouse gases, which they predicted would help students gain more accurate knowledge of the greenhouse effect. Before and after the lesson, they asked students to sketch a concept drawing describing the greenhouse effect. The authors compiled a list of common statements or ideas used in the students' drawings to form seven explanations or models to which students appeared to adhere. They compared the pre- and post-lesson concept drawings to see how student explanations of the greenhouse effect changed over the course of the lesson. The authors then used statistical analyses to compare the students' pre- and post-concept drawings and measure changes in their understanding of the greenhouse effect.

The researchers found seven common explanations for the greenhouse effect. The most correct explanation of the greenhouse effect, which was named “expert-like,” said that the earth emits longwave radiation, which is absorbed and remitted in random directions by greenhouse gas molecules. The second most correct explanation was named “molecular details,” which explained greenhouse gas molecules wiggling and emitting radiation in random directions. The other incomplete or incorrect explanations were “simple reflection” (solar energy reflects off of the earth and then re-reflects off of greenhouse gases); “trapping” (radiation emitted from the earth's surface is blocked by greenhouse gases); “improved reflection” (shortwave radiation from the sun is reflected off of the earth's surface as longwave radiation which is re-emitted by greenhouse gases); “layer” (greenhouse gasses form a layer that reflects solar energy); and “ozone” (solar radiation enters the atmosphere through holes in the ozone layer and is then reflected off of the earth's surface and the ozone layer).

Researchers found that students could easily add new ideas to their existing concepts of the greenhouse effect, like the idea of “longwave radiation.” Some ideas were easy for students to change and replace after the lesson, like the “layer” idea. Students who incorporated ideas about the behavior of greenhouse gas molecules tended to create the most accurate descriptions of the greenhouse effect.

The two incorrect ideas that were the stickiest, or less often abandoned by students, were the “trapping” and “ozone” explanations. The concept of “trapping” is commonly used to explain the greenhouse effect but implies that heat energy cannot escape the atmosphere. The “ozone” idea confuses the greenhouse effect with the ozone layer, which shields the earth from harmful UV radiation, and the ozone hole, which was caused by ozone depletion. Researchers specifically addressed the confusion with ozone at the end of the lesson, which may have helped some students improve their understanding of the greenhouse effect. Many students whose pre-lesson drawings used “ozone” or “trapping” as an explanation of the greenhouse effect, however, still did not depict a correct concept after the lesson.

The students did their post lesson diagrams of the greenhouse effect shortly after receiving the 30-minute lesson, so the results do not show how students' understandings changed long term. This study was conducted with students who had already had several weeks of introductory college level lessons on earth processes. Students that are more advanced or less advanced may have different existing conceptions of the greenhouse effect and may have different levels of change after a lesson. This study may also be difficult to apply in other settings because students of different ages and educational backgrounds may have different results.

When teaching about the greenhouse effect, talking about greenhouse gases on a molecular level may help students better understand the greenhouse effect. To improve the lesson, researchers recommend that educators address sticky incorrect concepts early in the lesson (rather than at the end) so that students have those misconceptions in mind while going through the lesson. For example, the “ozone” explanation of the greenhouse effect likely comes from confusion between greenhouse gases and the ozone layer. Lessons should address this confusion and clearly differentiate the greenhouse effect and the ozone layer. The authors admit that the “trapping” explanation of the greenhouse gas effect does connect carbon emissions to global warming. Although it reinforces incorrect ideas about the greenhouse effect, it may be appropriate for a less advanced audience to help them understand the importance of reducing carbon emissions.